Low-Cost Carbazole-Based Hole-Transporting Materials for Perovskite Solar Cells: Influence of S,N-Heterocycle

Diphenylamine-substituted carbazole (DPACZ) compounds are one of the most interesting hole transporting materials (HTMs) for perovskite solar cells (PSCs). However, most studies focused on the development of symmetrical DPACZ HTMs with two DPACZ arms or multiple ones. In this work, we developed a new class of asymmetric DPACZ-based HTMs (M111-114) through a combination of one DPACZ arm and different S,N-heterocyclic compounds (phenothiazine (PTZ) and dithieno-[3,2-b:2',3'-d]pyrrole (DTP)), which endow the M111-114 with different electrochemical and photophysical properties as well as hole-transporting properties. Results conclude that the PTZ outperforms of the DTP when combined with the DPACZ arm. In addition, we have investigated the substituent and conjugation effects of heterocyclic properties on the photophysical and electrical properties, as well as performance in PSCs by using physical measurements. PSCs with M114 exhibit a power conversion efficiency of 17.17%, which is higher or comparable to that of DPACZ HTMs with more than one DPACZ arm. Importantly, the synthetic cost of the M114 is only 14.95 $ per g, which is much lower than that of spiro-OMeTAD. This work indicates that DPACZ-heterocycle compounds could be a new class of low-cost HTMs in the large-scale application of PSCs.